A macromolecular elastic material basically is a material that has a flexible macromolecular structure or a material that has a structure formed by combining a rigid macromolecular part and a flexible macromolecular part. This macromolecular elastic material exhibits rubber elasticity at normal temperature, is plasticized at a high temperature similarly to a thermoplastic plastic, and can therefore be mechanically molded. This macromolecular elastic material is therefore used in a wide range of industrial fields. Examples of a typical macromolecular elastic material include those of a styrene type, an olefin type, a polyester type, a polyurethane type, a polyvinyl chloride type, a polyamide type, and the like.
These macromolecular elastic materials are usually provided as molded articles each produced by a mechanical operation such as extrusion. On the other hand, preferably, the macromolecular elastic materials are used each as an aqueous dispersion when the macromolecular elastic materials are each used in a coating agent for various types of material, a gluing adhesive, a binder, a thermal fusion bonding agent, a modifying agent for an emersion and the like, a convergence agent for a fiber, or the like.
Many researches have been conducted so far on the aqueous dispersion of the macromolecular elastic material and an aqueous dispersion of a styrene-type elastic material has been provided as a practical-use article. The aqueous dispersion of the styrene-type elastic material is usually produced by mixing with each other an organic phase formed by dissolving the styrene-type elastic material into an organic solvent and an aqueous phase formed by dissolving an emulsifying agent (a surface active agent) into an aqueous medium, emulsifying the mixture liquid using a homogenizing mixer or the like, and removing thereafter the organic solvent (for example, Japanese Laid-Open Patent Publication No. 51-23532 and Japanese Laid-Open Patent Publication No. 2003-253134).
The molded article acquired from the aqueous dispersion of the styrene-type elastic material, however, is in general inferior in the wear resistance, the flex resistance, the oil resistance, and the weather resistance. In contrast, the polyester-containing elastic material not only is better in these properties but also can provide a molded article that is produced therefrom and that has better properties also for the heat resistance, the flexibility, the low temperature property, and the high mechanical strength. The polyester-containing elastic material is useful as a material to produce, for example, items in the machine and the device fields such as a hose, a belt, and a packing, car parts such as a CVJ boot and a door latch, a sealing agent for connectors and sensors, and electric & electronic parts such as a cord cover and an antenna cover.
The aqueous dispersion of the macromolecular elastic material such as the styrene-type elastic material is generally acquired using a method according to which an organic phase formed by dissolving the macromolecular elastic material into an organic solvent and an aqueous phase formed by dissolving an emulsifying agent into an aqueous medium are mixed with each other, the mixture liquid is emulsified using a homogenizing mixer or the like, and the organic solvent is thereafter removed, or a method according to which the macromolecular elastic material and an aqueous phase formed by dissolving an emulsifying agent into an aqueous medium are mixed with each other and mechanical shear is applied to the mixture at equal to or higher than the temperature of the melting point of the macromolecular elastic material to emulsify the mixture. The former, however, involves problems such as the one that the load on the environment is significant because the former uses the organic solvent. The latter also involves problems such as decomposition of the resin due to the thermal history applied to the macromolecular elastic material and occurrence of any adverse effect on the adhesiveness due to the used emulsifying agent.